Lens forming method of composite optical film

Abstract

The present invention discloses a method for forming a lens of a composite optical film, which comprises the following steps: A molding die has an upper die base and a lower die base. The upper die base has an upper die core, and a lower end face of the upper die core forms an upper lens mold part. The lower die base has a lower die core, and an upper end face of the lower die core forms a lower lens mold part; An optical film sheet pre-heated to a softened state is disposed on the lower lens mold part; The optical film sheet is disposed on the lower lens mold part; A plastic supply mechanism injects metered molten plastic from above the center position of the optical film sheet; The upper die base and the lower die base are closed to form a lens forming space between the upper lens mold part and the lower lens mold part; After keeping the upper die base and the lower die base closed until the molten plastic is cooled, a lens with an optical film sheet can be made.

Description

Technical Field

[0001] The present invention relates to the manufacture of lenses, and particularly to a method for forming a lens with a composite optical film. Background Art

[0002] Please refer to Figure 7 , which shows the injection molding manufacturing method of existing optical lenses. Mainly, a molten resin material 8 is extruded into a molding die 9. The molding die has a cavity 91 and a runner 92 corresponding to the shape and size of the lens. The cavity 91 is communicated with the runner 92. The molten resin material is extruded through the runner 92 into the cavity 91 to form an optical lens.

[0003] In order to be applied in the virtual reality (VR) field, an optical film is disposed on the lens surface of the optical lens, so that light passes through the optical film to generate a magnified virtual image, providing an immersive experience for the user. Therefore, in the conventional injection molding of optical lenses, through the in-mold labeling method, an optical film 94 is first adsorbed on the inner wall of the cavity 91 through a suction channel 93 in the cavity 91, and then the molten resin material 8 is injected into the cavity 91, and the molding die 9 is maintained in a pressure-holding state and cooled to form a lens with an optical film.

[0004] However, since the optical film 94 is made of a soft material, when the molten resin material 8 is injected laterally into the cavity 91, it is easy for the molten resin material 8 to displace the optical film 94 or penetrate between the film 94 and the inner wall of the cavity 91, resulting in poor yield. In addition, if the middle part of the cavity 91 is too narrow, it will affect the smooth injection of the molten resin material 8 from one side to the other side, thereby limiting the center thickness of the lens and making it impossible to effectively thin the lens. And the suction channel 93 is only on one side of the cavity 91 and can only adsorb one optical film 94, unable to achieve the function of making a double-sided optical film.

[0005] In the optical device provided by Chinese Patent No. CN111413799, the optical film is directly disposed on the lens by coating or attaching, but the thickness of the glue used for bonding is not easy to control, or the coating is uneven, which will cause the glue layer to affect the light transmission path.

[0006] In addition, existing optical films must be pre-pressed and heated to form a curvature that conforms to the lens, resulting in an additional process in the production, and the production efficiency cannot be effectively improved. Summary of the Invention

[0007] The main object of the present invention is to provide a method for forming a lens of a composite optical film. The optical film is placed into the mold part from top to bottom and hot-melt plastic is injected. By closing the upper mold base and the lower mold base, a lens with the optical film can be directly formed without pre-pressing the film into a spherical shape in advance, so as to improve the production efficiency. Moreover, a lens with a double-sided optical film can be manufactured, and by injecting the hot-melt plastic from top to bottom, the effect of thinning the lens can be achieved.

[0008] To achieve the aforementioned object, the present invention provides a method for forming a lens of a composite optical film, which includes the following steps:

[0009] a. A molding die includes an upper mold base and a lower mold base disposed relatively below the upper mold base. The upper mold base has an upper mold core, and a lower lens mold part is formed on the end face of the upper mold core facing downward. The lower mold base has a lower mold core, and an upper lens mold part is formed on the end face of the lower mold core facing upward.

[0010] b. When the upper mold base and the lower mold base are separated, an optical film is placed on the lower lens mold part.

[0011] c. A plastic supply mechanism injects metered hot-melt plastic from above the central position of the optical film.

[0012] d. The upper mold base and the lower mold base are closed to drive the upper lens mold part and the lower lens mold part to approach each other, so as to form a lens molding space between the upper lens mold part and the lower lens mold part, and the average pressure of the hot-melt plastic is increased.

[0013] e. The upper mold base and the lower mold base are maintained in the closed state until the hot-melt plastic cools, so as to manufacture a lens.

[0014] Preferably, the optical film is pre-heated to a softened state.

[0015] Preferably, before the upper mold base and the lower mold base are closed, another optical film is placed on the hot-melt plastic. The upper mold base and the lower mold base are closed and maintained until the hot-melt plastic cools, so as to manufacture a lens with a double-sided optical film.

[0016] Preferably, the closing temperatures of the upper mold base and the lower mold base are 110°C to 120°C respectively. When the upper mold base and the lower mold base are separated, the upper mold base is heated and raised by 60°C to 80°C.

[0017] Preferably, the plastic supply mechanism uses low injection pressure (less than 200 kg / cm2) extrusion discharge.

[0018] Advantages of the present invention: In the present invention, an optical film is placed into a mold part from top to bottom and hot-melt plastic is injected. By closing the upper mold base and the lower mold base, a lens with an optical film can be directly formed, without pre-pressing the film into a spherical shape in advance, so as to improve the production efficiency. Moreover, a lens with a double-sided optical film can be manufactured. By injecting hot-melt plastic from top to bottom, the lens can be thinned. Description of the Drawings

[0019] Figure 1 It is a flowchart of the steps of the first embodiment of the present invention.

[0020] Figures 2 to 5 It is a schematic diagram of the operation of manufacturing a lens in the first embodiment of the present invention.

[0021] Figure 6 It is a schematic diagram of placing a film in the second embodiment of the present invention.

[0022] Figure 7 It is a cross-sectional view of an existing molding die. Detailed Description of the Invention

[0023] Please refer to Figures 1 to 5 , which is the first embodiment of the lens molding method of the composite optical film provided by the present invention. A molding die includes an upper mold base 1 and a lower mold base 2 disposed relatively below the upper mold base 1, wherein:

[0024] The upper mold base 1 has an upper mold core 11. The upper mold core 11 has a first cylindrical portion 12 extending downward. The outer contour of the first cylindrical portion 12 is cylindrical, and an upper lens mold portion 13 is formed on the downward end surface of the first cylindrical portion 12. Among them, the mold closing temperature of the upper mold base 1 is 110°C to 120°C.

[0025] The lower mold base 2 is provided on a base 5. The lower mold base 2 has a mold core hole 21 extending downward from its upper end surface. Taking the manufacture of a circular lens as an example, the inner edge shape (i.e., the cross-sectional shape) of the mold core hole 21 is circular, which conforms to the outer contour shape of the circular lens to be manufactured. The first cylindrical portion 12 is correspondingly received in the mold core hole 21 downward. The upper mold base 1 and the upper mold core 11 are synchronously driven by a transmission mechanism (not shown in the figure), so that the first cylindrical portion 12 can move up and down in the mold core hole 21. The lower mold base 2 has a lower mold core 22, and the lower mold core 22 has a second cylindrical portion 23 located in the mold core hole 21. An upper lens mold portion 24 is formed on the upward end surface of the second cylindrical portion 23. The outer contour of the second cylindrical portion 23 is cylindrical, which also conforms to the inner edge shape of the mold core hole 21. The lower mold core 22 is driven by a pushing mechanism (not shown in the figure), so that the second cylindrical portion 23 can also move up and down in the mold core hole 21. Among them, the temperature of the lower mold base 2 is 110°C to 120°C.

[0026] Please continue to refer to Figures 1 to 5 , which shows the step flow of actually manufacturing a lens for the first embodiment of the lens forming method of the composite optical film provided by the present invention. As Figure 2 shown, when the upper mold base 1 and the lower mold base 2 are separated, first heat the upper mold base 1 to a temperature of 170°C to 200°C, and place an optical film sheet 3 pre-heated to a softened state on the lower lens mold part 24; then as shown in Figure 3, a plastic supply mechanism 4 enters between the upper mold base 1 and the lower mold base 2 from the side, and aligns its injection port 41 with the center position of the optical film sheet 3, and injects the metered molten plastic from above the center position of the optical film sheet 3. By the extrusion pressure of the molten plastic, the optical film sheet 3 is fully attached to the lower lens mold part 24; then as Figure 4 shown, the upper mold base 1 and the lower mold base 2 are closed to drive the upper lens mold part 13 and the lower lens mold part 24 to approach each other, and a lens forming space 31 filled with molten plastic is formed between the upper lens mold part 13 and the lower lens mold part 24, and the average pressure of the molten plastic is increased; keep the upper mold base 1 and the lower mold base 2 closed. After the molten plastic in the lens forming space 31 is cooled and maintained in a pressure holding state through the upper mold core 11 and the lower mold core 22, a lens with an optical film sheet can be manufactured; finally as Figure 5 shown, open the upper mold base 1 upward to move the first cylindrical part 12 out of the mold core hole 21, and then move the lower mold core 22 upward to push the second cylindrical part 23 upward to eject the mold core hole 21, and then the manufactured lens with an optical film sheet can be taken out from the lower lens mold part 24.

[0027] It should be particularly noted that since the mold core hole 21 is an open space, the molten plastic will cool down faster than the plastic in a closed space in traditional injection molding. Therefore, the temperature of the molten plastic must be heated to 300°C; in addition, by heating the upper mold base 1 to a temperature of 170°C to 200°C first when it is separated from the lower mold base 2, the upper mold base 1 will not cool down below the temperature of the molten plastic while waiting for injection, which affects the lens forming.

[0028] In addition, the present invention adopts a low injection pressure (less than 200 kg / cm2) extrusion type for discharging materials, and the diameter of the injection port 41 is only slightly smaller than the diameter of the material pipe, which can avoid the problem that the plastic rotates and mixes with air when the plastic flows out of the injection port caused by the high pressure in conventional injection molding, so that the molten plastic can flow out smoothly from the injection port 41.

[0029] In the present invention, the hot-melt plastic is injected from above the central position of the optical film 3 by the plastic supply mechanism 4, so that the hot-melt plastic can diffuse outward from the central position of the optical film 3 and be evenly distributed on the optical film 3. Due to the injection impact force of the hot-melt plastic, the optical film 3 is pressed down, avoiding the lateral injection of plastic in the conventional injection molding, which easily causes the plastic to displace the film or penetrate between the film and the mold cavity, thereby improving the yield. By injecting the material from top to bottom and then closing the mold, the size of the lens forming space 31 can be adjusted to achieve the effect of thinning the lens. Moreover, due to the pressure of the hot-melt plastic during molding, the softened optical film 3 can be fully attached to the lower lens mold part 24 to form a spherical arc surface that conforms to the lens curvature, without pre-pressing the optical film 3 in advance, so as to achieve the effect of improving the production efficiency.

[0030] Please refer to Figure 6 , the lens forming method of the composite optical film provided by the present invention further has a second embodiment, and the difference between it and the first embodiment is that in this second embodiment, before the upper mold base 1 and the lower mold base 2 are closed, another optical film 3' is placed on the hot-melt plastic. Then, the upper mold base 1 and the lower mold base 2 are closed and kept closed until the hot-melt plastic cools, and a lens can be made. And both opposite sides of the lens surface are respectively provided with an optical film to achieve the function of making a double-sided optical film lens; in addition, in the second embodiment, when the upper mold base 1 and the lower mold base 2 are closed, the upper lens mold part 13 of the upper mold base 1 presses down the optical film 3', so that the softened optical film 3' can be fully attached to the upper lens mold part 13 to form a spherical arc surface that conforms to the lens curvature, and similarly, the optical film 3' does not need to be pre-pressed in advance.

Claims

1. A lens forming method for a composite optical film, characterized in that, It includes the following steps: a. A molding die includes an upper die base and a lower die base disposed relatively below the upper die base. The upper die base has an upper die core, and a lens mold part is formed on the end face of the upper die core facing downward. The lower die base has a lower die core, and a lens mold part is formed on the end face of the lower die core facing upward; b. When the upper die base and the lower die base are separated, an optical film is disposed on the lower lens mold part; c. A plastic supply mechanism injects metered molten plastic from above the center position of the optical film; d. The upper die base and the lower die base are closed to drive the upper lens mold part and the lower lens mold part to approach each other, so as to form a lens molding space between the upper lens mold part and the lower lens mold part, and increase the average pressure of the molten plastic. Before the upper die base and the lower die base are closed, another optical film is disposed on the molten plastic; e. The upper die base and the lower die base are maintained in a closed state until the molten plastic cools to form a double-sided optical film lens.

2. The lens forming method of the composite optical film according to claim 1, characterized in that, The optical film is preheated to a softened state.

3. The lens forming method of the composite optical film according to claim 1, characterized in that, The closing temperatures of the upper die base and the lower die base are 110°C - 120°C respectively. When the upper die base and the lower die base are separated, the upper die base is heated and raised by 60°C - 80°C.

4. The lens forming method of the composite optical film according to claim 1, characterized in that, The plastic supply mechanism uses low injection pressure extrusion for discharging materials.

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